Apparatus for controlling relative movement between a work tool and a workpiece

ABSTRACT

A WORKPIECE HAVING AN ARRAY OF OPENINGS IS PLACED ON A WORKHOLDER TO ALIGN THE OPENINGS WITH A LIKE ARRAY OF BORES IN THE WORKHOLDER. THE WORKHOLDER IS MOVED TO POSITION SUCCESSIVELY EACH OF THE OPENINGS IN THE WORKPIECE IN ALIGNMENT WITH A WORK TOOL WHICH IS ACTUATED TO INSERT A PART IN EACH OF THE OPENINGS TO A PREDETERMINED DEPTH. WHEN SELECTED ONES OF THE OPENINGS ARE ALIGNED WITH THE WORK TOOL, PINS PREPOSITIONED IN THE CORRESPONDING BORES   BLOCK A SENSOR ORIFICE TO ENERGIZE A FLUIDIC CIRCUIT AND OPERATE A DEVICE TO LIMIT THE TRAVEL OF THE WORK TOOL TO INSERT THE PART TO A DEPTH LESS THAN THE PREDETERMINED DEPTH.

June 1, 1971 D. J. PASSARELLA ETAL 3,581,370

APPARATUS FOR CONTROLLING RELATIVE MOVEMENT BETWEEN A WORK TOOL AND A WORKPIECE Filed May 28, 1969 2 Sheets-Sheet 1 JNVEI'NTUE'S I7. ..I PHE'E'HRE'LLH F7. J: PERRUTTH June 1, 1971 D. J. PASSARELLA ETAL 3,581,370

APPARATUS FOR CONTROLLING RELATIVE MOVEMENT BETWEEN A WORK TOOL AND A WORKPIECE Filed May 28, 1969 2 Sheets-Sheet z 47 48 I I 59 5/ FILTER /-?EGULATOR LUBR/CA TOR REGULA 7'01? REGULA TOP /5 r/6 84 as United States Patent 3,581,370 APPARATUS FOR CONTROLLING RELATIVE MOVEMENT BETWEEN A WORK TOOL AND A WORKPIECE Daniel .I. Passarella, Belleville, and Anthony J. Perrotta, North Haledon, N..I., assignors to Western Electric Company, Incorporated, New York, N.Y.

Filed May 28, 1969, Ser. No. 828,603 Int. Cl. H051: 13/04 US. Cl. 29-403 13 Claims ABSTRACT OF THE DISCLOSURE A workpiece having an array of openings is placed on a workholder to align the openings with a like array of bores in the workholder. The workholder is moved to position successively each of the openings in the workpiece in alignment with a work tool which is actuated to insert a part in each of the openings to a predetermined depth. When selected ones of the openings are aligned with the work tool, pins prepositioned in the corresponding bores block a sensor orifice to energize a fluidic circuit and operate a device to limit the travel of the work tool to insert the part to a depth less than the predetermined depth.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to a fiuidic apparatus for controlling the relative movement between a work tool and a workpiece, and more particularly, to a fluid logic circuit for controlling a travel impeding device to control the depth to which terminal screws are driven into a terminal board.

(2) Technical consideration and the prior art In the assembly of terminal screws and washers with terminal boards, it is sometimes necessary that selected ones of the terminal screws be driven into the board to a different depth than others. Some of the terminal screws are driven through washers and completely into the terminal board so that the head of the terminal screw engages the washers which are seated against a terminal attached to a top surface of the terminal board. Sometimes it is required that the head of the terminal screw be spaced a predetermined distance from the terminal board so that, for example, installers in the field may wrap a wire around the shank of the terminal screw.

Generally, in the assembly of terminal boards, a plurality of terminal screws are driven into the board by a semiautomatic terminal screw driving apparatus in which an operator moves the mounting board under a driving head, so that an array of openings in the terminal board are positioned in seriatim under the driving head. Then terminal screws are conveyed from a supply to the driving head for insertion into the openings in the mounting board.

However, in the conventional apparatus, all of the terminal screws are driven through the same predetermined distance or are all driven completely into the terminal board until the heads of the terminal screws engage the washers which are seated against the terminals on the top surface of the board. When the heads of the terminal screws are in engagement with the washers which are in engagement with the terminals, the torque applied by the drive head to the screw exceeds a predetermined value and the drive head is disengaged from the drive screw by a slip clutch and returned to an unoperated position in preparation for another cycle. Alternative, a mechanical stop may be used to impede the travel of the drive head after the 3,581,370 Patented June 1,, 1971 screws have been driven a predetermined distance or completely into the terminal board until the head of the screw engages the Washer which engage the terminals.

If all of the screws have been turned completely into the terminal board, it is then necessary for an installer in the field to manually unscrew selected terminal screws from the board until the heads thereof are spaced a predetermined distance from the board so that the bare end of a wire may be wrapped around the screw. Or the terminal boards with the terminal screws turned completely into the openings in the terminal board are processed through another work station. There, each of the selected screws which are to be only partially turned into openings in the board are turned manually to move the head thereof a predetermined distance from the terminal board. This process is time-consuming and is wasteful in that each of the terminal screws must be first turned completely into the openings in the board and then selected ones turned in a reverse direction to move the heads of the selected ones out of engagement with the terminals on the terminal board.

It is therefore an object of this invention to provide a fluid logic circuit for controlling the depth to which the terminal screws are driven into a terminal board.

SUMMARY OF THE INVENTION With these and other objects in mind, the present invention contemplates an apparatus for selectively controlling the distance traveled by a work tool relative to a workpiece at each of a plurality of work position on the workpiece as the workpiece is advanced indexably to move each of the plurality of work positions on the workpiece into alignment with the work tool.

More particularly, an apparatus for controlling a depth to which terminal screws are driven into a terminal board includes a workholder having a plurality of longitudinal grooves formed on an underside thereof and on which is placed a terminal board having an array of openings formed thereon. The openings in the terminal board are aligned with bores in the workholder so that as the workholder is moved along a guide rail to position each of the openings in the board in alignment with a work tool, each of the bores in the workholder is positioned in seriatim over a fiuidic sensor which is connected into a fluidic circuit that operates an air cylinder. The air cylinder is double acting and controls the movement of a travel impeding device into engagement with a collar attached to a drive shaft of the work tool. The workholder is preassembled with programming pins selectively placed in those bores that are aligned with the openings in the terminal board to which terminal screws are to be driven to only a predetermined depth. As the operator moves the workholder along the guide rail, the operator actuates the work tool as each of the openings is aligned with the work tool. Then as such of the pins is positioned over the fluidic sensor, the fiuidic circuit is energized to operate the air cylinder and move the travel impeding device into engagement with the collar on the drive shaft to limit the downward travel of the work tool, and hence, insert the terminal screw to only a predetermined depth within the opening in the terminal board.

Additional advantages and features of the invention will be better comprehended by reference to the drawings and detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of an apparatus for inserting terminal screws in a terminal board which is moved between positions shown in phantom and having a control system constructed in accordance with the principles of the apparatus of this invention for regulating the descent of a driving bit;

FIG. 2 is an enlarged detailed view in plan of a portion of a terminal board mounted on a workholder having a plurality of longitudinal grooves formed on the underside thereof, one of which is received on a guide rail on a worktable;

FIG. 3 is an enlarged view section of the workholder taken transverse to the longitudinal grooves to show an opening in the workholder into which a terminal screw is to be driven into seating engagement with a terminal secured to the terminal board, and showing another opening in the workholder into which a pin has been inserted in order to block a sensor orifice connected to a fluidic circuit to cause the fluidic circuit to operate an air cylinder to limit the downward travel of the driving bit; and

FIG. 4 is a schematic view of a fluidic circuit which is used to control the operation of the air cylinder to move a travel impeding device into engagement with a collar mounted on a drive shaft of the driving bit when one of the pins in the workholder is aligned with the driving bit and blocks the sensor orifice.

DETAILED DESCRIPTION Referring now to FIG. 1, there is shown an apparatus, designed generally by the numeral 10, for driving a terminal screw 11 to a predetermined depth into each of a plurality of openings 12 (see also FIG. 3) formed in an array of rows and columns in a terminal board 13. The terminal board 13 into which the terminal screws 11 are to be driven is preassembled with a plurality of terminals 14 having prongs which extend through the terminal board so that the terminals 14 are in engagement with a top surface of the board and the prongs protrude below a bottom surface of the board. The terminals 14 are pretapped to permit insertion of terminal screws 11 into the openings 12 in the terminal board 13. A pair of washers 15 are prepositioned in engagement with the terminals 14 in alignment with each of the openings 12 prior to insertion of one of the terminal screws 11.

The apparatus includes a work tool 31 (see FIG. 1) which is cylically operated to drive a terminal screw 11 into each of the openings 12 in the terminal board as the openings are successively positioned in alignment with the work tool. Also, as the openings 12 are moved into alignment with the work tool 31, the openings are aligned with a sensor orifice 26 which is connected through a fluid logic circuit 27 (see FIG. 4), that operates a travel impeding device 86 to limit the downward travel of the work tool. Normally, the terminal screws 11 are turned into the openings 12 until the headed ends thereof are in engagement with the washers which are supported on the terminals 14. For this condition, the fluid logic circuit 27 functions to convey air from a supply (not shown) and exit freely from the sensor orifice 26. As other selected ones of the openings 12, into which the terminal screws 11 are to be turned with the headed ends thereof spaced from the terminals, are moved into alignment with the sensor orifice 26, the sensor orifice is blocked by sensor elements 21 (see FIG. 3) to create a back pressure and render effective the fluid logic circuit 27 to operate the travel impeding device 86.

In order to support the terminal board 13 during the screw driving operation, the terminal board is placed on a workholder 16 having a plurality of stepped bores 17 formed therein in an array identical with the array of openings 12 in the terminal board (see FIGS. 1 and 3). The top surface of the workholder 16 is formed with a plurality of apertures for receiving the protruding prongs of the terminals 14 when the terminal board 13 is placed on the workholder 16 to align the openings 12 with the stepped bores 17. Also, the workholder '16 has a plurality of longitudinal spaced grooves 18 formed parallel to each other in the underside of the workholder with each of the grooves aligned with a column of the array of openings 4 12 (see FIG. 3). Each of the stepped bores 17 terminates in one of the grooves 18 in the workholder 16.

Prior to the assembly of the terminal screws 11 with the terminal boards 13, a sensor element or programming pin 21 is inserted into each of selected ones of the stepped bores 17 in the [WOIkhOldCI' 16, as shown in FIG. 3. These selected bores 17 are those into which the terminal screws 11 are to be driven to a depth such that the headed end of the terminal screw does not engage a terminal -14. Each of the sensor elements 21 is inserted with a shank portion thereof oriented upwardly with a top end of the shank portion spaced from the top end of the shank poriton spaced from the top surface of the terminal 14 on the terminal board 13 to permit insertion of a terminal screw 11 to the predetermined depth.

Referring now to FIG. 1, an operator places the workholder 16 on a worktable 23. The worktable 23 is formed with a guide rail 24 (see FIGS. 2 and 3) which is received in one of the grooves 18 of the underside of the workholder. The guide rail 24 is formed with two portions which are spaced apart as shown in FIG. 2, one on either side of a hole 25 on the table 23. A sensor orifice 26, connected to a fluid logic circuit (see FIG. 4), designated generally by the numerals 27, protrudes upwardly through the hole 25 in the table 23 so that the top open end of the orifice is approximately in a plane with a top surface of the guide rail 24 (see FIG. 3). When one of the stepped bores 17 having a sensor element 21 inserted therein is moved over the sensor orifice, the open end of the sensor orifice 26 is spaced from the lower surface of the headed end of the sensor element a distance not greater than 0.015 inch.

Then, the operator places a cover plate 28, having countersunk openings 29 formed therethrough in an array identical to the array of openings 12 in the terminal board 13, in engagement with the terminal board (see FIG. 3). The cover plate 28 is undercut to fit over the terminal board 13 and align the countersunk openings 29 with the openings 12 in the terminal board. Moreover, the countersunk openings 29 have a diameter sufficiently large to pass the washers 15 and hold the washers aligned and in engagement with the terminals 14 in preparation for the insertion of the terminal screws 11.

The operator moves manually the workholder 16 slide ably along the guide rail 24 on the top surface of the table 23, to the left as shown in FIG. 1, to position successively each of the openings 12 in each column in the terminal board 13 in alignment with a work tool, for example, a screwdriver, designated generally by the numeral 31, which is aligned with the hole 25 in the table and the sensor orifice 26. The work tool 31 is mounted on a frame 30.

Terminal screws 11 and washers 15 are supplied to the drive tool 31 and the cover plate 28, respectively for assembly with the terminal board 13. A supply chute 32 (see FIG. 1) has an exit end spaced above and sufficiently off-center from a vertical axis through an axis of rotation of the work tool 31 and the center of the hole 25 to permit the work tool to be moved downwardly to turn a terminal screw 11 into the opening 112 in the terminal board. The supply chute 32 conveys pairs of the washers 15 from a supply (not shown) into the countersunk opening 29 currently positioned in alignment with the Work tool 31.

A second chute 33 for supplying terminal screws 11 has, as shown in FIG. 1, an exit end adjacent an access opening in a split collet 34 of the work tool 31 when the work tool is in an unoperated, or up position. Terminal screws 11 are fed singularly from a supply 36 which is suspended from the frame 30 (see FIG. 1), and are released by an escapement 37 to fall through the opening into the collet 34 with the headed end of the terminal screw oriented upwardly. The escapement 37 is opened by a linkage 38 which is operated as the work tool is moved upwardly following the turning of a terminal screw 11 into an opening 12 in the terminal board 13. A typical arrangement of a power operated mechanism for assemblying threaded fasteners which shows screws fed from an escapement mechanism and through an access opening in one of a pair of opposed jaws and then driven into a workpiece by a drive tool is shown in US. Pat. 2,989,996 issued June 27, 1961 to P. H. Dixon.

Assuming now that an opening 12 into which a terminal screw is to be driven to a first depth until the headed end engages the washers '15 supported on one of the terminals 14 is in position under the work tool 31, the operator depresses a pedal (not shown) which actuates a control circuit (not shown) to release a pair of washers from the supply chute 32 into the countersunk opening 29 and to operate a drive shaft 39 (see FIG. 1) to turn a driving bit 41. Simultaneously, the driving bit 41 is moved downwardly to urge the terminal screw '11 in the collet 34, through the collet 34 and into the countersunk opening 29 in the cover plate 28 which is now in alignment with the work tool 31. The drive bit 41 turns the screw 11 into the opening 12 in the terminal board '13 until the headed end of the terminal screw is in engagement with the washers 15 supported on one of the termi male 14 on the board 13. As can best be seen in FIG. 3, there is adequate clearance around the lower end of the terminal screw -11; since the lower end of the terminal screw enters the large diameter portion of the stepped bore 17, the screw does not engage the workholder 16.

After the headed end of terminal screw 11 is in engagement with the washers 15 supported on the terminal 14, the torque applied to the work tool 31 exceeds a predetermined value and the control circuitry (not shown) disengages rotation of the work tool through a slip clutch (not shown) and moves the work tool upwardly. A typical torque control system for a power screwdriver is shown in the hereinbefore referred-to patent issued to P. H. Dixon.

As the work tool 31 is moved upwardly, the linkage 38 is operated to open the escapement 37 and release the leading one of the screws 11 to descend in the chute 33 and be received in the access opening in the collet 34 with the threaded end oriented downwardly and the headed end upwardly. In this way, the terminal screw 11 is oriented properly so that in the next cycle of operation, upon descent of the work tool 31, the drive bit 41 will engage the head of the screw and push the screw through the split collet 34 into the countersunk opening 28 then in alignment with the work tool.

The apparatus is also operated to turn terminal screws 11 a second depth into selected ones of the openings 12 in the terminal board 13 so that the headed ends of the terminal screws are spaced a predetermined distance above the washers which are supported on the terminals 14. When the operator moves one of selected openings 12 aligned with one of the stepped bores 17 in the workholder 16 which contains one of the sensor elements 21, over the hole 25, the sensor element is positioned over the sensor orifice 26 from which a fluid such as air from a supply (not shown) is normally emitted. Since the gap between the sensor orifice 26 and the sensor element 21 is no greater than approximately 0.015 inch, the positioning of one of the sensor elements over the sensor orifice 26, which is connected through a touch sensor 43 (see FIG. 4), creates a back pressure and renders effective the fluid logic circuit 27 to operate the travel impeding device 86. Alternatively, a proximity sensor device (not shown) could be used in which a plurality of jets of air converge at a point and which is rendered operative if the sensor element 21 is spaced 0.2 inch or less from the convergence point.

The fluid logic circuit 27 as shown in FIG. 4, includes the supply (not shown) of air which is moved over a conduit 46 through a filter 47 and a first regulator 48 to a junction point 49 at a pressure of approximately 90 lbs. per sq. in. From junction point 49, the air flows through a conduit 51 and a regulator 52 where the air pressure is reduced to approximately 10 lbs. per sq. in. and then continues through a flow control valve 53 to a commercially available fluid logic device 54, such as, for example, an OR/NOR device or a NOT device.

The fluid logic device 54 is a fluid logic element in which a power supply output is changed in response to a control input. As shown in FIG. 4, the fluid logic device 54 is constructed with a power supply opening 56 connected to the valve 53 and connected by a passageway 57 to a first output port 58. Control air is supplied off conduit 51 from a junction point 59 through a regulator 61 to reduce the air pressure to approximately 1 lb. per sq. in. and then through a passageway 62 of the touch sensor 43 to a flow control valve 63 and along a conduit 64 into a control input port 66 in the fluid logic device 54. The input port 66 is connected to the passageway 57 and intersects the passageway 57 at a point common with a passageway 68 that connects to a second output port 69.

In operation, if one of the sensor elements 21 is not aligned over the sensor orifice 26 to block the orifice, air flows from junction point 59 through the regulator 61 and touch sensor 63 and exits from the sensor orifice 26. In this normal unoperated state, air pressure is not present at input 66, and air flows from the power supply port 56 through passageway 57 to the first output port 58. However, if one of the sensor elements 21 is positioned over the sensor orifice 26, air flow therefrom is blocked and the air moves through the touch sensor 43 and the valve 63 over line 64 and to the input port 66. In response to control air present at the input port 66, the supply air flow is switched from the first output port 58 to the second output port 69.

The fluid logic device 54 is used to control the operation of a commercially available FLICR valve 71 with the output port 58 connected to a passageway 72 in the valve and the second output port 69 connected to a passageway 73 in the valve. The passageways 72 and 73 open to opposite ends of a chamber 74 which houses a slideably movable actuator 76. The actuator 76 is moved in either direction as shown in FIG. 4 by air flowing from one of the passageways 72 or 73. As the actuator 76 is moved in either direction, the actuator moves a pivotally mounted conduit 77. The conduit 77 is connected through a conduit 78 and lubricator 79 to the junction point 49 to supply air under a pressure of approximately to lbs. per sq. in. pressure to the FLICR valve 71. The conduit 77 pivots between two supply connections 81 and 82 to supply air to an air cylinder 83. Normally the FLICR valve 71 is in an unoperated condition, as shown in FIG. 4, so that air is supplied through the lubricator 79 and line 78 to the FLICR valve, and then out of the valve to the supply connection 81 of the double acting air cylinder 83 to maintain a piston 84 in a retracted position within the cylinder.

The fluid logic circuit 27 is responsive to one of the sensor elements being moved over the sensor orifice 26 to operate the double acting air cylinder 83. When one of the sensor elements 21 is positioned above and in close proximity of the sensor orifice 26, the air flow from the orifice is blocked to create a back pressure through the touch sensor 43. The back pressure in the touch sensor 43 causes the supply of control air at approximately 6 to 10 lbs. per sq. in. to flow along line 64 to the fluid logic device 54 to switch the fluid logic device and change the output from port 58 to port 69. As the air supply which normally maintains the actuator 76 to the right as shown in FIG. 4 is shifted to output port 69, air travels through the passageway 73 and urges the actuator 76 to the left. As the actuator 76 is moved to the left, the conduit 77 is moved pivotally in a counterclockwise direction, as viewed in FIG. 4,- to align with the cylinder connection 82 and air is moved into the cylinder 83 to urge the piston 84 to the left.

As the piston 84 is moved to the left, as shown in FIG. 4, a travel impeding device 86 (see FIG. 1) is moved to the left to position a yoke 87 about the periphery of the drive shaft 39. Then, when the operator depresses the pedal (not shown) to actuate the driving bit 41, the work tool 31 is moved downward until a collar 88 secured to the drive shaft 39 engages the yoke 87. In this way, the downward travel of the work tool 31 is interrupted or limited so that the terminal screw 11 is moved the second depth into the opening 12 in the terminal board 13 a distance which is less than that which occurs when one of the sensor elements 21 is not in alignment with the sensor orifice 26.

On the other hand, if one of the pins 21 is not positioned in alignment with the driving bit 41, the double acting air cylinder 83 is not operated and the travel impeding device 86 is positioned as shown in FIG. 1 so that the collar 88 engages a portion 89 of the travel impeding device and the terminal screw 11 is driven the first depth into the terminal board 13 so that the head engages the terminal 14 on the terminal board. It can be seen that the torque controlled slip clutch (not shown) described hereinbefore is not necessary in that the engagement of the collar 88 with the portion 89 of the travel impeding device 86 performs the same function.

After the operator has actuated the apparatus to drive a terminal screw 11 into one of the selected openings 12 in the terminal board 13, the operator moves slideably the workholder 16 along the guide rail 24 until the next successive opening 12 is positioned in alignment with the driving bit 41. As the operator moves the workholder 16 and the sensor element 21 away from the sensor orifice 26, air again escapes from the orifice so that the pressure in passageway 62 is reduced and bias is removed from the fluid logic device 54 so that air from the power supply (not shown) moves through passageway 72 to urge the actuator 76 to the right, or normal unoperated position. As the actuator '76 is moved to the right, the conduit 77 is moved pivotally in a clockwise direction as viewed in FIG. 4 to move from the supply port 82 to the port 81 of the double acting air cylinder 83 and move retractably the piston 84 within the air cylinder. As the piston 84 is moved to the right, the impeding device 86 is moved to the right as shown in FIG. 1 to position the portion 89 under the collar 88 so that the apparatus 10 is conditioned to drive the next successive terminal screw 11 completely into the next successive opening 12 in the terminal board 13. Should the next successive opening 12 be aligned with a stepped bore 17 that contains a sensor element 21, the above-mentioned cycle will be repeated when the sensor orifice 26 is blocked by the sensor element.

Should successive ones of the openings 12 in a particular schedule of terminal boards 13 be designed to have the terminal screws 11 only partially turned therein, the workholder 16 could be preassembled with a continuous sensor element or programming strip (not shown) which may be received in the groove 18 between those successive openings. In this way, the fluidic sensor orifice 26 is blocked continuously until the operator has moved the workholder so that the strip (not shown) no longer covers the orifice.

After the operator has successively positioned each of the openings 12 in one column of the array of openings in the terminal board 13, the operator disengages the workholder from the guide rail 24. Then the operator shifts the workholder 16 laterally of the worktable 23 until the next adjacent groove 18 in the workholder is aligned with the guide rail 24. Then the operator repeats the cycle of the operation and moves successively each of the openings 12 aligned with the next adjacent groove 18 in which the rail 24 is now received into alignment with the work tool 31.

It would be within the scope of this invention to provide a feed device which would advance the workholder 16 indexably to align successively each of the openings 12 in a column with the work tool 31. Moreover, modifications could be provided which could also shift laterally the workholder 16 to disengage the workholder from the guide rail 24 and then reengage the next adjacent groove 18 with the guide rail and repeat the cycle of operation to insert terminal screws 11 in the openings 12 in the column of openings aligned with the next adjacent groove 18.

It would also be within the scope of this invention to provide an apparatus having a work tool 31 which may be selectively moved through any of a plurality of different distances relative to a workpiece at each of a plurality of work positions. In the specific embodiment of this invention discussed hereinbefore, a terminal screw 11 could then be turned into an opening in the terminal board 13 to any selected one of a plurality of diiferent depths. This may be accomplished by using sensor elements 21 having differing dimensions which are inserted into the stepped bores 17 of the workholder 16 in accordance with a predetermined program of the depths to which the terminal screws 11 are to be turned. Each of the sensor elements 21 is dimensioned to cooperate with one of a plurality of sensor orifices 26 which protrude different distances above the worktable 23 to render effective the fluid logic circuit 27 and move one of a plurality of mechanical stops 86 into the path of travel of the collar 88.

This invention also comprehends the use of fluid logic devices 54 other than an OR/NOR logic element or a NOT element. For example, an AND/NAND logic element could be included so that a first sensor orifice 26 is normally blocked to create a back pressure and apply a control signal to one input of the AND/NAND element. The workholder 16 is programmed to include another sensor element 21' at each work position where a diflerent distance of travel of the work tool 31 is de sired. When the workholder 16 is moved into registration with the work tool 31, the other sensor element 21' blocks a second sensor orifice 26 and supplies a control signal to the second input of the AND/NAND element thereupon switching the power supply to operate the FLICR valve 7L Other combinations of sensor elements 21, mechanical stops 86 and fluid logic elements 54 to control the distance traveled by a work tool 31 with respect to a workpiece are within the scope of this invention.

What we claim is:

1. In a fabricating machine;

a workholder;

a tool;

means mounting said workholder and tool for relative movement with respect to each other;

normally unoperated means for limiting the extent of said relative movement; and

selectively settable means rendered elfective upon movement of said workholder for operating said movement limiting means.

2. In a system for controlling the extent of successive movements of a work tool with respect to a workpiece which is advanced to align successively each of a plurality of work positions on the workpiece with the work tool;

means for supporting said workpiece;

normally unoperated means for limiting the travel of said work tool relative to said workpiece; a sensor element prepositioned in said supporting means indicating a selected one of said work positions; and

means responsive to the alignment of one of said selected work positions with said work tool for detecting said sensor element to operate said travel limiting means.

3. In a system as set forth in claim 2, wherein:

said normally unoperated means includes;

travel impeding device mounted for engaging said work tool to limit the travel of said work tool relative to said workpiece;

a fluid logic circuit for operating said travel impeding device to engage said work tool; and

said detecting means includes sensor means connected to said fluid logic circuit and which in response to the alignment of one of said sensor elements with sensor means renders effective the fluid logic circuit to operate said travel impeding device.

4. In a system as set forth in claim 3, wherein:

said travel impeding device includes;

a stop selectively positionable to partially obstruct the movement of said work tool for limiting the extent of advance of said work tool with respect to said workpiece; and

pneumatically controlled means for positioning the stop to obstruct the movement of the work tool; and wherein said sensor means includes means for projecting a stream of air against said workholder;

said sensor element blocks said air stream when said selected work position is aligned with said work tool and said sensor element is aligned with said detecting means; and

said fluid logic circuit includes a pneumatic switch means actuated by the blocking of the air stream for operating the pneumatically controlled means to control the extent of movement of said work tool toward said workpiece.

5. In a system as set forth in claim 4, wherein:

said work tool is a drive head for turning terminal screws to a predetermined depth into each of an array of openings in a terminal board;

said supporting means is a workholder having a like array of openings formed therein and aligned with said openings in said terminal board; and

said prepositioned sensor elements are pins prepositioned in selected openings in said workholder corresponding to preselected openings in said terminal board into which said screws are to be driven to a depth less than said predetermined depth.

6. In a work fabricating machine having a tool relatively movable through a predetermined distance with respect to a workholder which is movable with respect to the tool, the improvement which comprises:

a plurality of spaced sensor elements on the workholder; and

means responsive to the movement of the workholder for sensing a sensor element and for selectively changing the extent of relative movement of the tool with respect to the workholder.

7. In an apparatus which includes a work tool that is moved a predetermined distance relative to a workpiece supported on a workholder that is advanced to successively align each of a plurality of work positions on the workpiece with the work tool, the improvement which comprises:

means for changing the distance moved by said work tool relative to said workpiece;

means for operating said changing means; and

means prepositioned on said workholder for selectively actuating said operating means. 8. In a work fabricating apparatus having a work tool that is moved a predetermined distance relative to a workpiece supported on a workholder which is movable with respect to the work tool to align each of a plurality of work positions with the work tool, the improvement which comprises:

means for arresting said work tool at selected work positions to limit the travel of said work tool to a distance less than said predetermined distance;

means for projecting a stream of air against said workholder;

means associated with each work position at which said work tool is to be moved relative to the workpiece a distance less than said predetermined distance for blocking the air stream; and

means responsive to the positioning of said blocking means in alignment with said work tool for operating said arresting means.

9. In a system for controlling the extent of successive reciprocating movements of a fabricating tool with respect to a workpiece;

means for reciprocating the tool;

means for interrupting the movement of the tool to reduce the extent of reciprocating movement of the tool;

a carrier for supporting the workpiece;

means rendered effective between successive reciproeating movements of the tool for incrementally advancing the carrier to position successive sections of the workpiece in the path of movement of the tool; and

means on the carrier associated with each of said sections of the workpiece for selectively controlling the interrupting means to control the extent of movement of the tool relative to each of said sections of the workpiece.

10. In a system for inserting parts to different depths in a plurality of openings in a workpiece;

a workholder for supporting said workpiece and having a plurality of bores aligned with the openings in said workpiece;

a work tool selectively moved toward said workpiece to insert one of said parts in each of said openings in said workpiece;

means for guiding said workholder relative to said work tool to successively position each of said openings in alignment with said work tool;

means selectively moved into engagement with said work tool for varying the distance traveled by said work tool toward said workpiece;

fluid circuit means for operating said varying means;

and

programming means prepositioned in selected ones of said bores in said workholder for rendering effective said fluid circuit means when one of said selected openings is in alignment with said work tool.

11. In an apparatus for selectively inserting com- 4 ponents at two dilferent depths in a series of positions on a workpiece;

a workholder for supporting a workpiece, the workholder having a plurality of sensor elements mounted thereon indicative of predetermined positions on the workpiece at which components are to be inserted at a first depth;

a mechanism having a tool for inserting components into the workpiece;

means for operating said mechanism to advance said tool to insert a component at a second depth;

selectively operable means for blocking the advance of the tool to limit the insertion of a component to the first depth;

means for guiding the workholder to successively align each of said positions with said tool; and

means responsive to sensing a senor element for operating said blocking means to limit the insertion of a component to said first depth.

12. In an automatic screw driving machine having a screw driving means which is cyclically moved a predetermined distance to seat screws in a series of holes in a workpiece;

a workholder for supporting a workpiece;

means for guiding the workholder to successively present each hole of the workpiece in alignment with the screw driving means;

a stop selectively positionable to partially obstruct movement of the screw driving means for limiting the extent of advance of a screw into a hole;

pneumatically controlled means for positioning the stop to obstruct the movement of the screw driving means;

means for projecting a stream of air against the workholder;

means associated with each hole that is to receive a 12 partially seated screw for blocking the air stream; a headed pin positioned in each of said stepped bores d which correspond to selected openings into which pneumatic switch means actuated by the blocking of screws are to be turned with said heads spaced the air stream for operating the pneumatically eonabove said terminal strips and with the head of the trolled means to control he partial seating of a pin spaced above a bottom surface of the workholder screw in the aligned hole. a distance slightly greater than the height of said 13. In an apparatus for moving a drive bit attached guide fail; to a shaft having a collar mounted thereon to turn a y SlideablY movable about Said shaft to engage terminal screws into each of an array of rows and said collar to limit the downward travel Of said drive columns of openings in a terminal board with the heads of the screws normally in engagement ith t i l a sensor positioned in said aperture in said workable strips attached to a top surface of the board and in which and eXteIlding from a p Surface of the WOrktable the terminal board is moved in a predetermined manner a distance Substantially equal t ght f Said to position successively each of said openings in alignguide rail; and ment with said driv bit; a fluidic circuit responsive to the movement of one a workholder for mounting said terminal board, said Of Said P in juxtaposition With Said Sensor f r workholder having a plurality of grooves formed moving slideably Said yoke around said shaft. in an underside thereof aligned with the columns of openings in said terminal board and having a like References Cited array of stepped bores formed therein which are aligned with said openings when said terminal board is mounted thereon;

UNITED STATES PATENTS a worktable having a guide rail formed on a top surface S Y1 thereof and aligned with said drive bit for guiding 3'279045 10/1966 e said workpiece under said drive bit when said workholder is placed over said guide rail to receive said guide rail in one of said grooves, said guide rail formed in two linear portions separated by an aperture formed through said worktable and aligned with said drive bit; 30

GIL WEIDENFELD, Primary Examiner 

